1. Field of the Invention
The present invention relates to a multibeam antenna capable of switching the directivity in multi-directions and is suitably used for a micro communication module implementing an information communication function, storage function, and the like, the micro communication module being attached to various electronic devices such as a personal computer, a mobile phone, or an audio device when used.
2. Description of the Related Art
For example, information such as music, voice, various data, image, or the like along with a recently ongoing progress of digitization of data, becomes easier to handle through the useof a personal computer or a mobile device. Further, such information is band-compressed by a voice codec technology or image codec technology and thereby environment in which the information is easily and effectively distributed to various communication terminals through a digital communication service or digital broadcasting is being put in place. For example, audio/video data (AV data) can be received even by a mobile phone.
For a data transmitting and receiving system, a simple wireless network system applicable even to a small-scale area is now utilized in homes and various locations. As the wireless network system, a 5 GHz narrow-band wireless communication system proposed in IEEE802.1a, a 2.45 GHz wireless LAN system proposed in IEEE802.1b, and a next generation wireless communication system such as a short-range wireless communication system called “Bluetooth” receive a great deal of attention.
In the case of an antenna having no directivity in characteristic direction, there arises a problem that communication quality may deteriorate due to the existence of an interference wave, which is generated at a building wall or the like due to reflection of radio waves in multiple wave environment where many radio waves exist.
Under the above situation, antennas having directivity in specified directions have gotten a lot of attention.
Among them, a phase array antenna using a plurality of phase shifters, and an adaptive array antenna which uses a plurality of transmitting and receiving systems to perform adaptive signal processing are proposed.
Further, as the directional antenna, a Yagi-Uda antenna, which is used for receiving TV broadcast waves and the like is available. As shown in FIG. 1, a Yagi-Uda antenna 100 has a radiator 111 which radiates radio waves, as well as a reflector 112 having a length slightly longer than that of the radiator 111 and a wave director 113 having a length slightly shorter than that of the radiator 111 disposed on both sides of the reflector 111, thereby exhibiting the directivity as shown in FIG. 2 (refer to, for example, Patent Document 1: Japanese Patent Application Laid-Open Publication No. 10-123142).
Further, a directivity control antenna system having directivity in the characteristic direction by arranging a plurality of Yagi-Uda antennas and switching between them is proposed (refer to, for example, Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2003-142919).